U.S. patent number 4,238,601 [Application Number 06/051,569] was granted by the patent office on 1980-12-09 for perfluorinated aliphatic phenoxy bisorthodinitriles and polyphthalocyanines therefrom.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to James R. Griffith, Teddy M. Keller.
United States Patent |
4,238,601 |
Keller , et al. |
December 9, 1980 |
Perfluorinated aliphatic phenoxy bisorthodinitriles and
polyphthalocyanines therefrom
Abstract
A bisorthodinitrile of the formula: ##STR1## wherein R' and R"
are perfluorinated alkyls having from 1 to 4 carbon at, and the
phenyl groups are attached at the para position. A
polyphthalocyanine resin is prepared by heating one or more of
these bisorthodinitriles at a temperature from about 260.degree. C.
to about 295.degree. C. These resins are particularly useful in
high-temperature structural composites used in high-temperature,
moist or corrosive environments.
Inventors: |
Keller; Teddy M. (Alexandria,
VA), Griffith; James R. (Riverdale Heights, MD) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
21972111 |
Appl.
No.: |
06/051,569 |
Filed: |
June 25, 1979 |
Current U.S.
Class: |
528/206; 528/166;
528/168; 528/353; 528/86; 558/420 |
Current CPC
Class: |
C08G
73/00 (20130101); C08G 73/06 (20130101); C08G
73/0672 (20130101) |
Current International
Class: |
C08G
73/00 (20060101); C08G 73/06 (20060101); C08G
073/06 () |
Field of
Search: |
;528/353,206,86,166,168
;260/465F |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3993631 |
November 1976 |
Griffith et al. |
4067860 |
January 1978 |
Griffith et al. |
|
Primary Examiner: Lee; Lester L.
Attorney, Agent or Firm: Sciascia; R. S. Schneider; Philip
McDonnell; Thomas
Claims
What is claimed and desired to be secured by Letters Patent of the
United States is:
1. A polyphthalocyanine resin having recurring units of the general
formula ##STR6## wherein R' and R" are perfluorinated alkyls having
from 1 to 4 carbon atoms, the phenyl groups are attached at the
paraposition, and M is a metal or salt or a mixture thereof.
2. A polyphthalocyanine resin as claimed in claim 1 wherein R' and
R" are perfluorinated methyls.
3. The polyphthalocyanine of claim 1 wherein said metal is selected
from the class consisting of chromium, molybdenum, vanadium,
beryllium, silver, mercury, aluminum, tin, lead, antimony, calcium,
barium, manganese, magnesium zinc, copper, iron, cobalt, nickel,
palladium, and platinum.
4. The polyphthalocyanine of claim 3 wherein said metal is selected
from the class consisting of copper, silver, and iron.
5. The polyphthalocyanine of claim 1 wherein said salt is selected
from the class consisting of cuprous chloride, cuprous bromide,
cuprous ferricyanide, zinc chloride, zinc bromide, zinc iodide,
zinc cyanide, zinc ferrocyanide, zinc acetate, zinc sulfide, silver
chloride, ferrous chloride, ferric chloride, ferrous ferricyanide,
ferrous chloroplatinate, ferrous fluoride, ferrous sulfate,
cobaltous chloride, cobaltic sulfate, cobaltous cyanide, nickel
chloride, nickel cyanide, nickel sulfate, nickel carbonate, stannic
chloride, stannous chloride hydrate, complex of triphenylphosphine
oxide and stannous chloride and mixtures thereof.
6. The polyphthalocyanine of claim 5 wherein said salt is selected
from the class consisting of cuprous chloride, stannic chloride,
stannous chloride hydrate, and ferrous fluoride.
7. The polyphthalocyanine resin of claim 2 wherein said salt is
stannous chloride.
Description
BACKGROUND OF THE INVENTION
The present invention pertains generally to high-temperature resins
and their precursors and in particular to perfluorinated aliphatic
phenoxy bisorthodinitriles and the cyano-addition resins
therefrom.
Fiber-reinforced composite materials which comprise carbon or
graphite fibers dispersed in a resin are replacing metal in many
structural applications because of weight savings, cost
effectiveness, better properties and a greater range of properties.
The greater range of properties of composites over metals arises
because the property variations of polymers are greater than that
of alloys. Another advantage of composites over metals is the new
design concepts made possible by the improved properties.
Many properties can be changed by modifying the polymer through the
addition of constituents in the primary chain or through the
additions of substituents to the primary chain. For example, the
addition of molecular constituents with known stiffness
characteristics to the primary chain can make the polymer extremely
stiff or flexible. Adding molecular substituents to the primary
chain can radically affect the surface properties of the composite
material. However, the overall range of properties is limited by
the properties of the polymer.
The variation in properties of the polymers commonly used in
composite materials is considerable, but numerous shortcomings
exist. For example, the most widely used resins are epoxies and
aromatic polyimides. Epoxy-based composites have a maximum service
temperature of about 120.degree. C., are quite brittle, absorb
water readily, and have a limited engineering reliability. Aromatic
polyimides have a higher maximum service temperature, are stiff,
absorb water readily, and have a very limited engineering
reliability due to trapped solvents and water which is a by-product
of the synthesis.
Recently, a new class of resins has been obtained by polymerizing
certain bisorthodinitriles. These resins have many properties which
are better than the properties of previously used resins, e.g.,
thermal stability and engineering reliability. The structure of
these resins has not been completely confirmed, but for the
following reasons, the principal mechanism of formation is
theorized to be phthalocyanine nucleation. As the
bisorthodinitriles polymerize, the color becomes progressively
darker green in the manner similar to phthalocyanines. The
polymerization is difficult to initiate and promote which indicates
the formation of a large and complex nucleus such as the
phthalocyanine nucleus from a large end group such as the
phthalonitrile group.
The first resins of this type were prepared from bisorthodinitriles
having an amide bridge between the two phthalonitriles. Examples of
which are disclosed in U.S. Pat. Nos. 4,056,560, 4,057,569, and
4,136,107 by James R. Griffith and Jacques G. O'Rear.
These resins with comparable structural strength have several
advantages over epoxies and polyimides as structural materials.
Their maximum temperature stability in an oxygen-containing
atmosphere is about 230.degree. C., a temperature that is over
100.degree. C. greater than that for epoxies. Water resistance as
measured by the water-soak method is much better than that for
epoxies. Some of the resins, depending on the bridging chain, have
a much greater elastic modulus than polyimide resins. These resins
have many other advantages over polyimides due to an absence of
solvents in their preparation, a lower water absortivity, and not
being thermoplastic with a low glass-transition temperature.
Although the properties of these resins are excellent, many
applications require resins with even better properties. For
example, structural materials in a high-pressure steam or
sulfur-containing gas environments require a resin having almost no
water absorptivity and being extremely resistant towards acidic
attack.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to synthesize a
perfluorinated aliphatic phenoxy bisorthodinitrile which is
polymerizable to a polyphthalocyanine.
A further object of this invention is to polymerize a
polyphthalocyanine having a maximum service temperature of about
300.degree. C. and having a water absorptivity of about 1 weight
percent as determined by the water-soak test.
Another object of the present invention is to polymerize a
polyphthalocyanine which hardens to a solid having an extremely low
surface energy and being resistant to acidic attack.
These and other objects are achieved by synthesizing a
bisorthodinitrile with a high fluorine content in the bridging
chain and polymerizing a polyphthalocyanine therefrom by heating at
a temperature in excess of the melting point of the
bisorthodinitrile.
DETAILED DESCRIPTION OF THE INVENTION
The resins of the present invention are characterized as
polyphthalocyanines primarily on the basis of the progressively
darkening of the green color as the resins are formed. Their
formation is difficult to initiate and promote. Also the
phthalocyanine formation is a reasonable mechanism in view of the
dinitrile end groups of the precursor. It is on this basis that the
phthalocyanine formation is believed to be the principal reaction.
Other cyano-addition reactions may also be present; however, the
resulting resin is a three-dimensional network polymer with
exceptional uniformity in properties.
The resin with phthalocyanine nuclei has a structural formula:
##STR2## wherein ##STR3## represents a phthalocyanine nucleus, R'
and R" represent unbranched perfluorinated alkyls having from 1 to
4 carbon atoms, and the phenyl groups are attached at the para
position.
If the phthalocyanine is co-ordinated by a metal or salt, the
polyphthalocyanine nucleus is represented by ##STR4## wherein M
represents a metal and MX represents a salt. A more detailed
formula of both phthalocyanine nuclei are as follows: ##STR5##
Hereinafter, the resins of the invention are designated as
(PcO.sub.4 .phi..sub.4 (CR'R").sub.2).sub.n if neat, (M.PcO.sub.4
.phi..sub.4 (CR'R").sub.2).sub.n if coordinated with a metal and
(MX.PcO.sub.4 .phi..sub.4 (CR'R").sub.2).sub.n if coordinated with
a salt.
The most preferred resin has R' and R" as perfluorinated methyls.
The properties of the resin are comparable to the other compounds
of this invention, but the synthesis utilizes the readily prepared
and relatively inexpensive hexafluoroacetone bisphenol A.
The preferred metals for coordinating the resin are copper, iron,
zinc, and nickel due to their availability, handling, desired
reactivity and the enhanced thermal stability of the resulting
resins. Examples of other metals which may be used are chromium,
molybdenum, vanadium, beryllium, silver, mercury, tin, lead,
antimony, calcium, barium, manganese, magnesium, cobalt, palladium,
and platinum. The preferred metallic salt for coordination is
stannous chloride. This salt increases the reaction rate the most
and has the least trouble with poor dispersion and voids caused by
entrapped gas. These advantages occur only if the stannous chloride
is dispersed by the method described hereinafter. Other suitable
metallic salts include cuprous bromide, cuprous cyanide, cuprous
ferricyanide, zinc chloride, zinc bromide, zinc iodide, zinc
cyanide, zinc ferrocyanide, zinc acetate, zinc sulfide, silver
chloride, ferrous chloride, ferric chloride, ferrous ferricyanide,
ferrous chloroplatinate, ferrous fluoride, ferrous sulfate,
cobaltous chloride, cobaltic sulfate, cobaltous cyanide, nickel
chloride, nickel cyanide, nickel sulfate, nickel carbonate, stannic
chloride, stannous chloride hydrate, a complex of
triphenylphosphine oxide and mixtures thereof. Additional examples
of metals and salts are found in Mosher, Frank H. and Thomas,
Arthur L., Phthalocyanine Compounds, N. Y. Reinhold, 1963, p.
104-141.
The bisorthodinitriles, from which the present polyphthalocyanines
are polymerized can be prepared by stirring a perfluoroketone
bisphenol, 4-nitrophthalonitrile, and an excess amount of anhydrous
potassium carbonate or sodium hydroxide in dry dimethyl sulfoxide
(DMSO) at a temperature from room temperature to 90.degree. C. for
about six to eighteen hours under inert conditions. The listed
bases and solvent are given as examples. Other bases such as
lithium or potassium hydroxide may be used and other solvents, e.g.
dimethyl formadid would be satisfactory. Upon completion of the
reaction, the reaction liquid is filtered to obtain the
bisorthodinitrile. The end point is determined by any conventional
technique, e.g., ir-analysis.
The perfluorinated bisphenols can be easily prepared by reacting
phenol with a perfluorinated acetone. Symmetrical perfluorinated
ketones or those terminating at one end with a perfluorinated
methyl group can be prepared by the method which comprises reacting
a perfluorinated alkene with iodofluoride, reacting the product of
the previous step with chlorosulfonic or fluorosulfonic acid to
form a sulfonate, and reacting the sulfonate with cesium fluoride
to form the perfluorinated ketone. Unsymmetrical perfluorinated
ketones as well as symmetrical ones can be prepared by reacting a
perfluorinated epoxy with a Lewis acid, e.g., AlCl.sub.3.
Additional information concerning reactions involving fluorides may
be obtained from Chambers, Richard D. Fluorine in Organic
Chemistry, N.Y., Wiley Interscience, 1973.
The bisorthodinitriles can either be polymerized in one step or
stepwise to distinct stages. In either case, polymerization of the
present bisorthodinitriles is extremely difficult and requires the
polymerization temperature to be near the decomposition temperature
of the resulting resin. Temperatures below 260.degree. C. cause the
neat polymerization to take many days. Consequently, the
bisorthodinitriles must be heated to a temperature from about
260.degree. C. to about 295.degree. C. in order to have the
polymerization completed within a reasonable time. The atmosphere
can be oxygen-containing, inert, or a vacuum. Regardless of the
temperature, the heating is continued until the melt solidifies to
an extremely hard material. Often a post cure at a temperature up
to 295.degree. C. is used to improve the strength of the resin.
By the preferred method, the material is reacted to the B-stage as
a distinct step before it is polymerized to the C-stage. The method
comprises heating a bisorthodinitrile to about 250.degree. C. to
about 295.degree. C. until the viscosity starts to increase due to
the onset of the phthalocyanine formation which is called the
B-stage. At the B-stage, the material can be cooled to a frangible
solid and can be stored indefinitely without further reaction. The
C-stage is obtained from the B-stage resin by breaking up the
B-stage resin and heating the resin at a temperature from
260.degree.-295.degree. C. The preferred temperature for reacting
the resin to the C-stage is from 280.degree. C. to 290.degree. C.
The optimum cure for any particular resin at a particular
temperature is determined empirically by testing the structural
strength of samples over a range of cure times.
Adding a metal or salt substantially enhances the reaction rate.
Stannous chloride enhances the reaction rate the most, reducing the
reaction time from many days to a few hours in some cases.
In adding a metal or salt to co-ordinate the phthalocyanine nuclei,
the metal or salt is added in a stoichiometric amount while the
bisorthodinitrile is molten or powdered. If the amount of metal or
salt is less than stoichiometric, i.e., less than one equivalent
per two equivalents of the bisorthodinitrile the resulting resin is
not completely coordinated with the salt or metal. An amount in
excess of stoichiometry would cause the resin to have unreacted
metal or salt in it. Avoiding the presence of any unreacted salt or
metal is particularly important with the synthesis of the present
resins on account of the high temperatures needed for
polymerization.
High temperatures further require a high degree of purity on
account of the increased reactivity of all species present
including the impurities. The preferred amounts of impurities are
less than 100 ppm. However, impurities can be present in amounts up
to 300 ppm without noticeably affecting the quality of the final
resin.
As with previous polyphthalocyanine resins, the dispersion of the
salt or metal is affected by the particle size. Since the resin is
formed at such high temperatures, dispersion becomes particularly
critical. Consequently, particle sized up to 1000 micrometers are
preferred.
If stannous chloride is used to co-ordinate the resin, the stannous
chloride must be introduced into the melt as stannous chloride
dihydrate by the following method. The stannous chloride dihydrate
(SnCl.sub.2.2H.sub.2 O) is added as a melt or powder. If the
phthalonitrile is a powder, the mixture is heated, while being
stirred, to a temperature from the melting point to about
20.degree. C. in excess thereof until all water is expelled from
the mixture and if the phthalonitrile is molten, then the mixture
is kept at the melt temperature until all water is expelled. The
mixture is then reacted either to the B-stage or C-stage in the
manner previously described.
Examples of the preparation of bisorthodinitriles and
polyphthalocyanines of this invention are herein given. These
examples are given by way of explanation and are not meant to limit
the disclosure of the claims to follow in any manner.
EXAMPLE 1
Synthesis of Bisorthodinitrile of Hexafluoroacetone Bisphenol A
Using Potassium Carbonate As Base
A mixture of 10.1 g (0.03 mol) of hexafluoracetone bisphenol A,
10.4 g (0.06 mol) of 4-nitrophthalonitrile, 12.4 g (0.09 mol) of
anhydrous potassium carbonate and 60 ml of dry dimethyl sulfoxide
was stirred under a nitrogen atmosphere at 70.degree.-80.degree. C.
for 6 hours. The cooled product mixture was poured into 300 ml of
cold dilute hydrochloric acid. The pale brown product was collected
by suction filtration and washed with water until the washings were
neutral. The crude material was recrystallized from acetonitrile to
give 13.8 g (78%), m.p. 230.degree.-233.degree. C. of the desired
product.
EXAMPLE 2
Synthesis of Bisorthodinitrile of Hexafluoroacetone Bisphenol A
Using Sodium Hydroxide As Base.
A mixture of 67.2 g (0.2 mol) of hexafluoracetone bisphenol A, 16.5
g (0.4 mol of 50%) aqueous sodium hydroxide, 300 ml of dimethyl
sulfoxide and 75 ml of benzene was stirred at reflux for 15 hours
under a nitrogen atmosphere and the water which formed as a
by-product was removed with a 8 can-Stark trap. The benzene was
removed by distillation and 69.4 g (0.4 mol) of
4-nitrophthalonitrile was added to the reaction mixture at room
temperature. The resulting dark mixture was stirred at room
temperature for 12 hours under a nitrogen atmosphere. The cooled
mixture was then poured into 800 ml of cold water and the pale
brown product was collected by suction filtration.
Recrystallization from acetonitrile yielded 107 g (91%) of product,
m.p. 230.degree.-232.degree. C.
EXAMPLE 3
Polymerization of Bisorthodinitrile of Hexafluoroacetone Bisphenol
A
A sample (1.6 g) was placed in a planchet and heated at 280.degree.
C. for 7 days. After 3 days at this temperature, the melt began to
thicken. On the 4th day, gelation had occurred. The sample was
postcured for 3 days to ensure complete polymerization and to
toughen the polymer.
EXAMPLE 4
Polymerization of Bisorthodinitrile of Hexafluoroacetone Bisphenol
A in the Presence of Stannous Chloride Dihydrate
A sample of the monomer (0.51 g, 0.9 mmol) and stannous chloride
dihydrate (0.09 g, 0.4 mmol) was placed in a test tube and heated
at 250.degree. C. for 24 hours. After the sample melted, the sample
turned green and became homogeneous immediately. The viscosity of
the sample increased rapidly with gelation occurring in 15
minutes.
Samples prepared by a method similar to Example 3 was heated at
280.degree. C. for over 2500 hours in air. At 1600 hours, the
weight loss was about one percent of the original total weight. At
2000 hours, the rate of loss began to accelerate rapidly. Water
absorptivity of the samples were tested by the water-soak method.
Similar samples, i.e., of the neat resin were submerged in water
for 2800 hours. The water absorption was about one percent of
sample weight at 300 hours in the water. At 2800 hours, the water
absorption rose to only 1.1 weight percent. The neat resins have
been proven to be self-extinguishing. A sample prepared by a method
similar to Example 3 was placed in a flame with a temperature of
about 550.degree. C. until combustion had become evident. Upon
removal, the combustion immediately stopped.
As these tests demonstrate, the resins of this invention with a
bridge having a fluorocarbon and phenoxy moities have exceptional
thermal and oxidation resistance along with almost no water
absorptivity. Another important feature of these resins, which
increases the safety of their use, is that they are
self-extinguishing.
Obviously many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *